Revisiting Poinsettia Cold Finishing Up North

As growers, we continue to look for methods to reduce costs while still producing high-quality crops. This is especially true when growing poinsettias, as margins continue to grow thin and competition gets stronger. Growing poinsettias at cool temperatures has emerged as an option over the past several years to reduce heating costs.

The University of New Hampshire and Purdue University have been conducting research on a method we call cold finishing. Instead of turning down the thermostat for the entire production cycle of the crop, the temperatures are lowered during the latter portion of the cycle only, when the bulk of the heating costs are incurred. This also allows you to take advantage of the naturally warm temperatures in August, September and early October to bulk up plants before initiating short days.

How Cold Finishing Works

In the trials we’ve conducted, plants were grown according to a traditional crop schedule from potting until October 15. At this time, plants were moved to greenhouse zones with three different average daily temperatures (ADT). For more information on our growing protocols, visit GreenhouseGrower.com to read our July 2009 Greenhouse Grower article “Cold Finishing Up North.”

If you are not familiar with the term ADT, it is the average temperature plants are exposed to over a 24-hour period. For example, for 12 hours (7 a.m. to 7 p.m.) the greenhouse temperature is 75°F during the day and for 12 hours (7 p.m. to 7 a.m.) the temperature is 67°F, resulting in an ADT of 71°F. Why wait until October 15 to lower the temperatures?

In New Hampshire and Indiana, it is reasonable to obtain these temperatures after mid-October. Before this, it is difficult to maintain this low of a daytime temperature. The lower ADT is maintained throughout the remainder of the cropping time.

How Money Can Be Saved

Cost, of course, is one of the most important factors when evaluating if cold finishing will work for you. To estimate the difference in heating costs when cold finishing at three different temperatures, we used Virtual Grower (free software developed by the USDA). Table 1 shows the difference in heating costs when growing poinsettias in a 96- by 34-foot double-poly hoop house in either Concord, N.H., or Indianapolis, Ind. For the Indianapolis example, the grower would save $1,081 (28 percent), finishing at an ADT of 62°F starting on October 15–rather than an ADT of 71°F.

Table 2 (page 34) summarizes the savings for a crop grown in a 100- by 440-foot (roughly an acre) gutter-connected glasshouse in the same locations. In this case, a grower in Concord would save $19,280 (21 percent) using an ADT of 62°F versus 71°F. You can estimate the cost savings for your own operation by downloading Virtual Grower at http://www.ars.usda.gov/Research/docs.htm?docid=19961. Virtual Grower is also available in Spanish at the same website.

Which Cultivars To Grow

Which cultivars to grow is a complicated question. Let’s first take a look at the research done at The University of New Hampshire and Purdue University. In 2009, ‘Advent Red,’ ‘Christmas Eve,’ ‘Christmas Feelings,’ ‘Early Glory,’ ‘Early Orion,’ ‘Early Prestige,’ ‘Orion’ and ‘Viking’ were evaluated at three different finishing ADT over three different planting dates. Rooted cuttings were received and planted into 6.5-inch pots on week 31 (July 27), week 32 (Aug 3) and week 33 (Aug 10).

Once planted, they were grown at day/night temperatures (12 h/12 h) of 75/67°F (ADT or 71°F) and a 16-hour photoperiod provided by high-pressure sodium lamps, until the start of short days on October 1.

On October 15, plants were moved to zones with day/night temperatures (12 hr/12 hr) of 75/67°F (ADT 71°F), 70/62°F (ADT 66°F) or 68/56°F (62°F). These temperatures were determined based on the results from the previous year’s studies, indicating they would produce a high-quality crop. The plants were evaluated weekly for height, for first color and at finish for bract area, anthesis (first pollen shed) and marketability date.

At the end of the study, plants were given a rating based on overall quality and appearance. This rating was determined by calculating the ratio of bract area to plant height. Using this type of a rating system, a plant that had a high bract area for its height would obtain a high rating, while a tall plant with a small bract area would receive a low rating (Figure 1).

Cultivar is not the only factor to consider when using the cold finishing production method. You must also consider the planting week (which influences plant development before October 15) and the ADT (which influences plant development after October 15).

We have developed a series of charts to help you determine how to factor in all three of these variables to make a decision. These charts segregate our ratings by the finish heights of the cultivars trialed. Figure 2 (page 30) illustrates the combinations of planting week, cultivar and ADT that resulted in finished plants between 14 and 17.9 inches tall (from the bench to the top of the plant).

For the combinations resulting in finished plants between 18 and 19.9 inches and 20 and 25 inches go online to GreenhouseGrower.com. To use these charts, first determine the target height for your finished plants. For an example, we’ll use a target height of 16 inches with a tolerance of + 2 inches and use the chart for plants finishing between 14 and 17.9 inches (Figure 2). Next, to determine the quality rating that you wish to obtain at our cold finishing temperatures (ADT of 62 or 66°F), we’ll use between 20 and 24. That will result in the following options: ‘Viking’ or ‘Early Glory’ planted on week 33 and finished at 62°F ADT, or ‘Advent Red,’ Early Orion,’ ‘Orion,’ ‘Viking’ or ‘Early Glory’ planted on week 33 and finished at 66°F.

Note that the quality rating used here is biased toward shorter plants with relatively large bract areas. Each grower should determine what quality rating they want to target on this particular scale: this may be dependent on clientele.

Remember that the finished height of your crop is dependent on factors in addition to cultivar, greenhouse temperature and plant week. Growers may obtain different results depending on PGR use, as well as outdoor temperatures and light levels in a given year. Note that no plant growth regulators were used in this study. It is recommended that growers use these charts as a starting point but conduct their own trials to determine what combinations result in the desired finished plant.

If your operation produces plugs or liners for wholesale growers, please take a few minutes to participate in Greenhouse Grower’s 2016 Young Plant Grower Survey. We know you are very busy and we value your time and input. This survey should only take a few minutes. Greenhouse Grower’s Young Plant Grower Survey has played a key role in building our Top 20 Young Plant Growers list over the years. The information helps us zero in on trends taking shape and the challenges you’re facing as young plant growers. If you have any questions about this survey or you are not the right contact for this at your operation, please email me at [email protected], or please forward the survey link to the appropriate person. We would like to wrap up this survey by July 25, so please take it soon! Thank you in advance for your participation. We value your opinion! » […]

If your operation produces plugs or liners for wholesale growers, please take a few minutes to participate in Greenhouse Grower’s 2016 Young Plant Grower Survey. We know you are very busy and we value your time and input. This survey should only take a few minutes. Greenhouse Grower’s Young Plant Grower Survey has played a key role in building our Top 20 Young Plant Growers list over the years. The information helps us zero in on trends taking shape and the challenges you’re facing as young plant growers. If you have any questions about this survey or you are not the right contact for this at your operation, please email me at [email protected], or please forward the survey link to the appropriate person. We would like to wrap up this survey by July 25, so please take it soon! Thank you in advance for your participation. We value your opinion! » […]

Green Circle Growers in Oberlin, Ohio, has a commitment to using production practices that are efficient and sustainable. The operation has been growing Orchids for nine years, and is entering its second full year with its current system, which entails three camera grades. “The camera grading — first at production into a 5-inch pot, then 12 weeks later and a final grade after the stem and buds have developed — is raising our overall quality,” says Wesley Van Wingerden, director of growing for Green Circle Growers. Greenhouse Grower visited the operation to take a tour of its facilities and learn more about its Orchid production. Read on for more details about the process. The first of the camera grades is incorporated into the transplant process, which involves placing the Orchids from a community tray into 5-inch pots. The plants are separated into three sizes with the smallest returning to the […]

The tenth largest cuttings farm in the world, Vivero Internacional was founded in 1991 and began exporting unrooted cuttings in 1993. Based in Tepoztlan, Morelos, just outside of Mexico City, Mexico, the operation opened with 2 hectares or 5 acres. With time and new customers, the farm has experienced rapid growth, now spanning 40 hectares or 99 acres, says Vivero’s Dennis Hitzigrath. “The first 10 years, production was doubling every season,” Hitzigrath says. “In the last three years, it’s been about 20%.” The independent operation grows 100 million cuttings annually for several breeders, serving the North American market. Hitzigrath says consolidation among breeders has brought more of a focus on Vivero Internacional from third-party breeders in recent years. This growing interest is spurring even more growth. “We are planning for a minimum growth of 20%,” Hitzigrath says. “We are adding more production space and hope to be needing more […]

Mike’s Backyard Nursery sits on a long, narrow, 5-acre property located in Perry, Ohio. There, customers can find a variety of flowering shrubs available, all in 2-quart pots, and all for sale for $5.97 each. Owner Mike McGroarty, a lifelong resident of Perry, says the town has a lot of plant nurseries, including 100 wholesale growers within a 10-mile radius of his house. That doesn’t discourage McGroarty, because he knows that while there are a lot of nurseries in his area, no one else is doing what he is doing. McGroarty has learned about plants — and marketing them to his audience — through decades of experience. He has never hesitated to pass along his knowledge to other growers looking to start their own backyard operations, and has created an entire program to educate aspiring growers. McGroarty Likes To Practice What He Preaches McGroarty’s operation serves as the laboratory for […]

As most growers know well, the federal government regulates all insecticides, fungicides, herbicides and other commercial chemicals used on agricultural crops. Therein lies the problem with use of chemicals on cannabis crops – so far, the feds want nothing to do with legalized marijuana. According to “Concern Grows Over Unregulated Pesticide Use On Cannabis,” a June 17 article on the National Public Radio (NPR) network by Agribusiness Reporter Luke Runyon, the lack of regulated chemicals for cannabis has left growers to experiment on their own. “In the absence of any direction the subject of pesticide use on the crop has just devolved to whatever people think is working or they think is appropriate,” said Colorado State University Entomologist Whitney Cranshaw in the NPR report. “Sometimes they’ve used some things that are appropriate, sometimes unsafe.” Denver officials held tens of thousands of marijuana plants earlier this year due to safety concerns, but […]

A researcher from North Carolina State University (NC State) has found that in the case of the flame azalea (Rhododendron calendulaceum), all pollinators are not created equal. In fact, due to the flower’s unique reproductive structure, butterflies — and specifically, their wings — are the key to pollination. The flame azalea is commonly found in the Appalachian Mountains, ranging from as far north as New York to Georgia in the south. Like most azaleas, the flowers are large, and have an unusual structure: both the anther (male) and stigma (female) parts are very elongated and separated from one another. NC State biologist Mary Jane Epps was interested in how the azalea’s flower structure affected its pollination. “In order for a plant to reproduce, a pollinator — usually an insect — has to spread the pollen from the anther to the stigma,” Epps says. “In the case of the flame azalea, […]

The Horticultural Research Institute will grant $125,000 in financial support for four key projects as part of the Horticultural Industry Bee & Pollinator Stewardship Initiative. The Initiative has three primary goals. First, to convene a task force to develop a bee and pollinator stewardship program, including creation of best management practices for plant production. Second, to identify and fund research that will help answer key science questions and fill gaps needed to design and refine the stewardship program. Third, to seek to positively position the horticultural community and its customers by collaborating with other compatible groups interested in augmenting pollinator habitat and protection.

If you are pursuing a floriculture research project, now is the time to apply for funding through the American Floral Endowment. Research pre-proposal applications for 2015-2016 funding are due to AFE by June 1, 2015.